Chemistry 112
First Hour Exam
Name:____________
(4 points)
Please show all work for partial credit
All problems are worth 12 points
1. How many significant figures are there in each of the following numbers:
____4____ 1.045
___4_____ .005009
____4____ 6.906x10-3
___8_____ .0056007800
___3_____ 95,200
_infinite__ 12 (in the conversion factor: 12 = 1 dozen) (Exact conversion)
2.Below are the results of four different calculations. Round the given answers to
reflect the proper number of significant figures
Calculation
Calculator Answer
Answer with correct
Answer
# of Significant Figures
A. 6000 + (2/8)
6000.25
__6000__________
B. 3.14x10-1 + 3.14x10+1
31.714
___31.7_________
C. Using the formula: Volume = l × w × h
where l = 2.50 cm, w = .0050 cm and h = 10300. cm
Volume=2.50×.0050×10300.
128.75
____130_________
D. Using the formula: Circumference = 2 ð r
where r = 2.50 cm and ð = 3.1415
Cir = 2(3.1415)2.50
15.7075
____15.7________
2
3.Perform the following unit conversions:
156 nm to cm
5.75 lbs to mg
The acceleration of gravity 9.8 m/s2 to ft/min2
4.What is the difference....
...between a homogeneous mixture and a heterogeneous mixture?
Both are mixtures, but in a heterogenous mixture you can see the individual components
in the mixture by eye, but in the homogeneous mixture you cannot.
...between a homogeneous mixture and a pure substance?
You cannot see any individual components in either, but in a homogeneous mixture there
are at least two different components, while in a pure substance there is only a single
component
...between a compound and an element?
A compound is a pure substance that contains at least two different kinds of atoms bonded
together in some way. An element is a pure substance that contains only one kind of
atom.
...between an atom of one element and the atom of another element?
Atoms of different elements differ by the number of protons in the nucleus.
...between an atom of one isotope of carbon and an atom of a different isotope of
carbon?
Atoms of different isotopes of carbon vary in the number of neutrons in the nucleus.
3
5.Fill in the following table:
# Protons
# Neutrons
11
17
12
18
54
77
# Electrons
Symbol
Metal or
Nonmetal
Name of
family on
Periodic
Table
12
Na- *
Metal
Alkali metal
18
Cl-
54
Xe
Nonmetal
Halide
Nonmetal
Noble Gas
* Sorry - my bad. Na is usually a + ions with 10 electrons. But as long as I had given
you 12 electrons, I thought I would see who took the answer to the correct ion charge.
6. Below are some names or that I have seen on chemistry tests or on chemical bottles
that may or may not be correct. Write the formula that would correspond to each name,
then, if the name is wrong, write the correct name.
Given name
Formula
Correct name
Manganese dioxide
_MnO2___
Manganese(IV) oxide
Calcium(II) chloride
_CaCl2___
Calcium Chloride
Iron oxide
FeO2 or Fe2O3
Iron(II) oxide or
Iron(III) oxide
Nitrogen(III) hydride
NH3_____
Ammonia or
Nitrogen trihydride
Hydrosulfuric Acid
H2SO4____
Sulfuric acid
Since the names on the left were incorrect, I accepted several different formulas
depending on the error you think was made in the name. As long as the correct name on
the right was consistent with the formula you gave, you got full credit for that name.
4
7. Below are the formulas for some chemical compounds. Write the correct name for each
formula
Rb2O
Rubidium oxide
Mo(NO2)3
Molybdenum(III) nitrate
SiH4
Silicon tetrahydride
P2 O 5
Diphosphorous pentaoxide
HBr
Hydrobromic Acid
H2SO3
Sulfurous Acid
I didn’t take off points if you didn’t know Rubidium or Molybdenum! (This time)
8. I was stymied this weekend at Walmart when I tried to buy popcorn. Orville
Redenbacher boxes proudly tell you that the box either contains 10-1.5 oz single
serving bag or 10-3.3 oz double serving bags. On the other hand, Pop Weaver brand
just tells you it has 24 bags, but it doesn’t tell you the size of the bag.
A. If the Pop Weaver box had a net weight of 3.4 lbs, how many oz. are there in each
bag?
B. In Mexico a case of Orville Redenbacher costs 412.08 pesos. Each case contains 12
boxes, and each box contains three - 3.3oz bags. What is the cost of Orville Redenbacher
in dollars/pound, if the current exchange rate is 1 peso = .07717 dollars?